[Merge] lp:~ahayzen/webbrowser-app/dnd-tabs-001 into lp:webbrowser-app/staging

[Andrew Hayzen]

Updated to resolve most of the issues found while doing the peer review on Friday :-)

I think the only things left for stage 1 are:
- writing autopilot test specifically testing that the correct urls are moved
- changing the way the tab delegate is animated when dragging down (so that it 'sticks' more to the bar)
- resolving what happens when/if we go into narrow mode
- investigating what firefox/chrome do when dragging tabs (do they have a special mime type)
-- 
https://code.launchpad.net/~ahayzen/webbrowser-app/dnd-tabs-001/+merge/308507
Your team Ubuntu Phablet Team is requested to review the proposed merge of lp:~ahayzen/webbrowser-app/dnd-tabs-001 into lp:webbrowser-app/staging.